Improvement of hybrid polyvinyl chloride/dapsone membrane using synthesized silver nanoparticles for the efficient removal of heavy metals, microorganisms, and phosphate and nitrate compounds from polluted water

Heavy metals exist in different water resources and can threaten human health, inducing several chronic illnesses such as cancer and renal diseases. Therefore, this work dealt with the fabrication of highly efficient nanomembranes based on silver nanoparticle (Ag NP)-doped hybrid polyvinyl chloride (PVC) by dapsone (DAP) using an in situ method. Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis were used to confirm the hybridization of PVC as well as the crystalline structure of hybrid PVC nanocomposites. Three varying proportions of Ag NPs (i.e., 0.1, 0.2, and 0.3%) were used to fabricate hybrid PVC-DAP nanomembranes. The Brunauer–Emmet–Teller (BET) method was used to estimate membrane surface area, porosity and distribution of pore volume. The mechanical strength and antibacterial properties of the cased films notably improved when Ag NPs were added depending on the NP ratio inside the matrix. Results obtained from adsorption experiments of PVC-DAP nanomembranes at 35 °C revealed that the optimum nanomembrane was achieved at 0.2% NPs and its percentage of removal effectiveness ranged from 71 to 95% depending on the ion type. The surface morphology of the PVC-DAP-0.2 Ag NPs before and after the adsorption process of the metal ions was analyzed using SEM-EDX. Moreover, the impact of other parameters such as the initial concentrations, pH media, temperature, and contacting time, on the adsorption efficiency of PVC-DAP-0.2 Ag NPs was also investigated. Furthermore, kinetic and adsorption isotherm models were suggested to describe the adsorption efficiency of the PVC-DAP-0.2 Ag NP membrane, and the uptake mechanism of metal ion removal was studied. The obtained outcomes for these fabricated nanomembranes demonstrated that they could be potential candidates for water purification and other potential purposes including biomedical areas.


Introduction
For the time being, the consumption of water resources is continuously increasing, and the water contamination issue is worsening. 1Thus, chronic diseases based on polluted water by heavy metals are considered a major threat to human health and the environment due to the augmenting morbidity rate of such diseases globally.Among these diseases, cancer and chronic renal illnesses can harm human organs when these metals exceed their safe limits.Heavy metals exist in various sources including ground water resources and environmental pollutants, where the former is the main factor for irrigation worldwide.][4] Accordingly, prolonged body exposure to these metals when they exceed the safe limits induces severe diseases such as cancer, neurodegenerative disorders, and hemochromatosis (i.e., iron overload), in addition to chronic renal illnesses. 5,6To tackle these shortcomings, nanomembrane-based smart polymeric matrices have been developed to enhance the removal of heavy metals from water resources and provide safe water owing a Polymer Metrology & Technology Department, National Institute of Standards (NIS), Tersa Street, El Haram, P.O.Box 136, Giza 12211, Egypt.E-mail: hesham.moustafa21@gmail.com;Fax: +20 2338 6745 1; Tel: +20 0173 4580 0 to innovative nanomembranes for living on a healthy planet.Huge efforts [7][8][9] have been made to explore these membranes as viable and cost-effective nanomembrane manufacturing.Regarding renal diseases, the kidney is considered the rst attack organ by heavy metal toxicity that causes acute renal failure, leading mostly to death.
PVC is a synthetic plastic that is extensively utilized in various applications such as pipes, cable insulation, and medical apparatus because of its exceptional properties comparable with other synthetic thermoplastics. 10It possesses high strength and good physical and chemical properties, in addition to thermal stability. 11Furthermore, PVC is an inexpensive polymer with high resistance to chemicals, lm forming ability, and good solubility in diverse organic solvents.In addition to its amazing PVC characteristics, it is an interesting polymer for membrane fabrication.Efforts [12][13][14] have been made on PVC-based membranes for oily wastewater remediation.Besides PVC properties, Ghaedi et al. 15 fabricated a PVC membrane as an optical sensor for detecting cupper ions (Cu 2+ ) in different water resources.Aryanti et al. 16 developed ultraltration nanomembrane-based PVC/polyethylene glycol reinforced with zinc oxide nanoparticles for river water remediation.Similarly, some studies [17][18][19][20] have been conducted to blend or hybridize PVC with materials to achieve the processability and other properties of the PVC matrix.For instance, Fang et al. 21fabricated a positively charged nanomembrane from PVC-graed-poly(N,N-dimethylaminoethyl methacrylate) using a crosslinking reaction for multivalent ion removal.However, Cai et al. 22 prepared highly efficient separation membranes by incorporating inorganic nanomaterials inside the PVC matrix to enhance overall membrane efficiencies.Therefore, the graing or hybridizing of PVC by these kinds of matters contributed to the rebirth of new alternatives for PVC matrices with sustainable properties.Therefore, (4,4 diaminodiphenyl sulfone) or dapsone (DAP) was utilized as a hybridizing material for the PVC matrix.Based on the DAP structure, it is considered a dual action as an antibiotic and anti-inammatory therapy. 23,24A study by Williams et al. 25 reported that DAP was the most widespread therapy for leprosy victims globally.Kawabata et al. 26 studied the inuence of ultraviolet (UV) lights and sunlight on the photodegradation of DAP in the aquatic medium.Moustafa et al. 24 developed a decorated bioagent from DAP-capped TiO 2 to boost the properties of the polyvinyl alcohol to be used in food-safe packaging and UV-shielding for biomedical purposes.Thus, the presence of primary amino groups in the DAP renders it highly reactive with several nanoparticles and polymer matrices to create new hybrid nanocomposites with amazing performance for end use materials. 27At present, Ag NPs have attracted great interest in the fabrication of antimicrobial and antifouling polymeric membranes. 8,28They are efficiently active in hindering the growth of a broad range of different microbes, including bacteria, fungi and viruses, through their interaction physically with microbe walls and media, resulting in cell death. 29,30Additionally, they can be used as reinforcing material inside polymeric matrices. 31A study by El Shehawy et al. 32 reported that Ag NPs have the potential as bio-adsorbents to eliminate heavy metals from contaminated water.However, Ag NPs mostly tend to form agglomeration structures into the polymer matrix. 33To tackle the nanoller agglomeration problem inside the matrix, the graing of polymer or nanoller treatment is necessary.To the best of our knowledge, no study has reported Ag NPs embedded in the hybridized PVC-DAP nanomembranes.Furthermore, sonication was employed in the nanomembrane preparation approach to achieve better homogeneity inside the membrane matrix.Consequently, this study focuses mainly on fabricating effective nanomembranes from Ag NPs doped inside hybrid PVC-DAP polymers to improve the removal of toxic metal ions and other biological impurities from water resources at an affordable cost.
In the present study, a facile hybridization of the PVC matrix using DAP material to obtain a hybrid PVC-DAP polymer was successfully performed.Varying ratios of Ag NPs were utilized as reinforcing agents in the PVC-DAP matrix to improve the nanomembrane properties and their long-term stability.The structure of hybrid PVC-DAP and the fabricated nanomembranes were investigated using FT-IR and XRD comparable with virgin PVC and pure DAP.The tensile, antibacterial and absorption efficiency properties of hybrid nanocomposites were metered.Moreover, the morphology of the optimized nanomembrane was assessed before and aer the uptake of toxic metal ions through SEM-EDX visualization.The isotherm and kinetic models of adsorption removal efficiency and the uptake mechanism for PVC-DAP-0.2Ag NPs were also discussed.

Hybridizing PVC by dapsone
Herein, hybridizing PVC by DAP was prepared by applying the in situ method as follows: 10 g of PVC was dissolved in a three-neck round ask containing 100 ml of THF under magnetic agitation until the complete dissolution of the polymer.Next, 3 g of DAP was dispersed in 50 ml ethanol and drop-wised into the polymer solution within approximately 30 min.Aerward, the mixture reuxed at 65 °C for 12 h with continuous agitation, as displayed in Fig. 1.Then, the mixture was cooled to ambient temperature and coagulated in distilled water, followed by triple rinsing with ethanol (70%) to eliminate the unreacted DAP and HCl as a byproduct.The obtained graed PVC-DAP was dried in a laboratory oven at 70 °C for 6 h.Aer the drying stage, the nanomembrane-based hybrid PVC-DAP-doped Ag NPs were fabricated by dissolving 136 mg of PVC-DAP in 50 ml of THF with agitation for complete dissolution at 60 °C, then, three varying contents of Ag NPs (i.e., 0.1, 0.2, and 0.5 wt%) were utilized and separately added to the dissolved polymer.The admixture was maintained under stirring for 15 min, followed by sonication for 10 min to fulll the embedment of the Ag NPs and their dispersion inside the PVC-DAP matrix.The previous system was kept in an ice bath to avoid solvent evaporation.Thereaer, the obtained admixture was decanted in a 70 mm diameter glass Petri plate and le in the dark overnight under normal conditions to evaporate the solvent.The thickness of each cast lm was adjusted by taking the same poured volume.
Aer drying, the nanomembrane lms were pulled off from the glass plates and kept in a laboratory desiccator for characterization and testing.The unlled PVC and PVC-DAP matrices were also prepared, as mentioned above for comparison.The fabricated nanomembranes were coded based on the ratio of Ag NPs in the PVC-DAP matrix, such as PVC-DAP-0.1 Ag NPs, PVC-DAP-0.2Ag NPs, and PVC-DAP-0.3Ag NPs.

X-ray diffraction
The structure of pure DAP and hybrid unlled polymer, as well as the morphology of absorbent lms reinforced with Ag NPs, were metered using a Malvern Panalytical, 3rd generation Empyrean X-ray diffractometer equipped with Cu Ka radiation (45 kV, 40 mA, and l = 0.15418 nm).The data were scanned over a 2q range from 5 to 85°with a step size of 0.05 and at a counting time per step of 2 s per step for powder specimens, 0.013°for nanomembrane lms, and at a sampling width of 0.010°. 35The crystallite size (D) of Ag NPs in terms of the peak width (hkl) for nanomembranes was determined using the Scherrer equation as follows: , K is a constant that is very close to unity, l is the X-ray wavelength, b is the width at half maximum (FWHM), and q is the diffraction angle.Additionally, hybridizing PVC by DAP and the lled nanocomposite lms were veried using Bruker LUMOS II (Bruker, Hamburg, Germany).The FT-IR spectra were recorded with OPUS soware, version 8.2, using the attenuated total reection mode in the spectral range of 600-4000 cm −1 with a resolution of 4 cm −1 and 64 scans. 36

SEM analysis
The surface morphology of the optimized nanomembrane before and aer the metal ion adsorption process was investigated using scanning electron microscopy/Energy-dispersive Xray spectroscopy (SEM Quanta FEG; EDX, Thermo scientic, dry/wet EDX).The fractured surfaces of the casted lms were coated with a thin gold layer before the examination to avoid any electrostatic charging during observation. 37

Mechanical properties
The tensile strength and elongation at break for casted absorbent lms were conducted using a Zwick (Germany) universal tensile testing machine (Model Z010) equipped with a load cell of 100 N and a crosshead speed of 100 mm min −1 , in accordance with ASTM D 882-18 standard.The dumbbell specimen's preparation and its environmental conditions were adjusted as described elsewhere. 36,38The mean value of ve replicates for each lm was recorded.

Brunauer-Emmet-Teller (BET)
An essential method for determining the specic surface area and pore size of PVC-DAP and PVC-DAP-0., and urea were prepared separately.To optimize the best sample available for element removal, about 0.1 g of each nanomembrane (virgin PVC, PVC-DAP), and their lled lms (i.e., PVC-DAP-0.1 Ag NPs, PVC-DAP-0.2Ag NPs, and PVC-DAP-0.3Ag NPs) was examined with 50 ml of 10 mg L −1 of element ion concentration at an appropriate pH for 120 min.When adjusting the adsorption conditions, the aqueous dilution of the stock solution created 50 ml of various element ion (5, 10, 15, 25, and 30 ppm) concentrations.Furthermore, the effects of changing the pH from 5 to 7.2 using 0.1 M NaOH and HCl solutions and contact times between 15 and 120 min were studied.Additionally, the impact of three temperatures (25, 35, and 45 °C) on the uptake of elemental ions was investigated.All the uptake tests were performed using an automated shaker at 160 rpm (Fig. 4(a)).When estimating the ability of element ions to be adsorbed, the variation in the concentrations of element ions in the solution before and aer the uptake test and the weight of the optimal sample stated in mg g −1 were all considered.For the subsequent computations, each adsorption process received an average of three repetitions.
The following equations were used to compute the removal efficacy (Q%) and the adsorption capacity of the adsorbent, which covered the time interval from time t (q t ) to stability time q e : where m is the mass of the adsorbent (g), V is the volume of the adsorption material (adsorbate) solution (L), and q t (mg g −1 ) is the quantity of element uptake on the adsorbent's unit mass at a time (t).The element ion concentrations C 0 and C t (mg L −1 ) are measured before and aer uptake at time t, which ranges from 15 min to equilibrium time.2.7.2. Regeneration and reuse study.Through desorption testing, the mechanism of contaminant removal and the reusability of the element ions can be readily recognized.We investigated the leaching/desorption of several element ions from aqueous solutions using DI water and 0.1 M of both NaOH and HCl.A recyclable PVC-DAP-0.2Ag NP membrane was generated by frequently washing it in DI water, which exposes it to four series of adsorption and desorption, and then constantly shaking it for 30 min at 25 °C at 160-170 rpm.The regeneration of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 , and urea into the PVC-DAP-0.2Ag NP membrane to eliminate different contaminants was evaluated many times using batch adsorption/desorption tests with 50 ml of 10 mg L −1 of the selected element ions at an acceptable pH ranging from 5 to 7.2 under automated shaking at 160 rpm at room temperature.Before immersing the regenerating PVC-DAP-0.2Ag NP membrane, the pH of the solution was adjusted.A similar process was used to evaluate the regenerated element ions and subsequent adsorption/ desorption cycles.The regeneration efficacy (RE%) was calculated using the following equation: where q de represents the quantity desorbed by each uid and q ad represents the amount adsorbed during loading.2.7.3.Application of the collected water samples using a PVC-DAP-0.2Ag NP membrane.From the New Valley Governorate in Egypt, one groundwater specimen was taken to be tested using a PVC-DAP-0.2Ag NP membrane.The residual solution was then retested aer a 50 ml sample of the collected polluted samples was equilibrated with 0.15 g of the created PVC-DAP-0.2Ag NP membrane for 120 min at 30 °C.
The Langmuir isotherm indicated a surface with uniform binding sites, equal sorption energies, monolayer adsorption, and no interactions between the adsorbed species.These were the most crucial presumptions for applying the Langmuir isotherm, such as the adsorbents (atoms, molecules, or ions) bonded to the active sites in precisely localized locations; only one substance was adsorbed at a time at each site, and each substance's energy level was constant across the entire surface regardless of what was adsorbed nearby.
One of the early correlations for irreversible and non-ideal adsorption was the Freundlich isotherm.Freundlich asserts that the adsorption region of an adsorbent surface is heterogeneous.This empirical relationship assumes that the heat and interest in adsorption were not spread uniformly across the adsorbent surface.Instead of single adsorption, this isotherm may be employed for multilayer adsorption.One of the key factors determining an adsorbent's efficacy is its adsorption kinetics, which characterizes the solute absorption rate by regulating the diffusion process and the residence duration of an adsorbate at the solid/solution interface.The pseudo-2ndorder kinetic model was concentrated on chemical adsorption, while the pseudo-1st-order kinetic model emphasized physical adsorption.The Temkin isotherm described the interactions between the compounds that were adsorbed.The values of each molecule's adsorption energy in an aqueous phase were considered when creating this isotherm model.This isotherm assumed that, disregarding the lower and upper concentration sets, the adsorption heat of all molecules in the layer decreases linearly with the active attachment sites as a function of temperature.The solute transfer in a solid-liquid sorption process is oen characterized by either intraparticle diffusion, exterior mass transfer (boundary layer diffusion), or both.Adsorption at both the outer surface of the adsorbent and the transport of metal ion molecules from the bulk into its pores is possible.Either intraparticle diffusion (IPD) or lm diffusion could be the adsorption rate-limiting stage. 40Adsorbates (metal ions) were carried to the adsorbent's exterior by lm diffusion, whereas intraparticle diffusion occurred when adsorbates moved inside the adsorbent's pores.The slower of the two is the rate-determining step because they operate in succession.Using the following Weber-Morris equation (Table S1 †), the potential for metal ion species to permeate into the inner spots of the adsorbent lm (PVC-DAP-0.2Ag NP membrane) was investigated: 41 Table S1 † depicts the IPD model expression and the intraparticle diffusion coefficient K diff .
To solve adsorption systems that highly produce rectangular isotherms and gain insight into the homogeneous energy distribution, the (D-R) adsorption isotherm empirical equation was specically designed.The slope of the linearized isotherm equation, which provided information about the adsorption mechanism, was used to determine the adsorption energy.The model was typically used to distinguish between the mean free energy and the physical and chemical binding processes of the element cations.The effects of temperature on the adsorption of the chosen element onto the PVC-DAP-0.2Ag NP membrane were investigated, and thermodynamic parameters (DG, DH, and DS) that described feasibility, spontaneity, and the type of adsorbate-adsorbent interactions were determined using the mathematical relationships shown in Table S1.†

Antibacterial assay
Klebsiella pneumonia (K.pneumonia) and Staphylococcus aureus (S. aureus) were chosen to represent G − bacteria and G + bacteria, respectively.The procedure for assessing antibacterial activity was conducted using the agar disc diffusion procedure, as reported elsewhere. 29,36At least duplicates were taken for each specimen.

FT-IR analysis and X-ray diffraction
Fig. 2(a) and (b) illustrate the zeta potential of synthesized Ag NPs and their particle size distribution metered using Malvern Zetasizer (Ver.7.02). 6The stability of the Ag NPs in the solution was found to be good, as their zeta potential was a negative value (−19.6 mV), with a mean particle size distribution in the range of 30-35 nm, indicating uniform particle dispersion in the aqueous solution. 30Fig. 3(a) demonstrates the FTIR spectra of virgin PVC and its hybrid by DAP in which the main absorption peaks for virgin PVC are located at ∼616 cm −1 and 648 cm −1 assigned to C-Cl stretching. 42Similarly, other absorption peaks were observed at ∼2912-2854 cm −1 , corresponding to the symmetric and asymmetric vibrations of -CH and -CH 2 , respectively. 43,44For hybrid PVC, new characteristic peaks appeared at ∼3395-3225 cm −1 , which signaled the NH-groups in DAP.Meanwhile, the disappearance of C-Cl peaks aer the hybridization process was observed.All of them evidenced that the hybridization of PVC by DAP was achieved.For nanocomposite lms, no signicant changes were observed in the FTIR regions when Ag NPs were added, indicating the physical character of Ag NPs inside the polymer matrix.Additionally, ESI † about the hybridization process and chemical interaction between the PVA-DAP matrix and Ag NPs was provided by XRD patterns, as depicted in Fig. 3(b).Moreover, the spectrum attributed to virgin PVC and pure DAP was obtained for comparison with the PVC-DAP matrix.As depicted in Fig. 3(b), there were no sharp diffraction peaks in the XRD pattern for virgin PVC, evidencing its amorphous structure. 34,45owever, sharp diffraction peaks with different intensities were observed for pure DAP at ∼2q = 17.13°, 19.71°, 21.25°, 22.86°, 24.10°, and 29.60°, indicating its crystalline state. 23However, these peaks almost disappeared when DAP reacted with the PVC matrix to form the hybrid PVC-DAP, conrming that the hybridization of PVC by DAP was achieved.When incorporating Ag NPs into PVC-DAP, different peaks of 2q appeared at ∼38.25°, 44.30°, 64.46°, 77.40°, and 81.02°, which were assigned to the Ag NPs in the matrix. 46,47Based on the Scherrer equation, it can also be observed that the crystallite size (D) of the indexed hkl (111) plane was estimated for PVC-DAP-0.1 Ag NPs, PVC-DAP-0.2Ag NPs, and PVC-DAP-0.3Ag NPs and was found to be 9, 11, and 17 Å, respectively.Thus, the fractional reduction in crystalline character and increase in crystallite size of Ag NPs in the XRD patterns of the polymeric membranes may indicate better incorporation and dispersion of Ag NPs into the membrane matrix.This result agrees well with the mechanical data.

Mechanical properties
The impacts of the Ag NP loadings on the tensile properties of hybrid PVC-DAP nanomembranes at different proportions (i.e., 0.1, 0.2, and 0.3 wt%) are illustrated in Table 1.The mechanical parameters in terms of tensile strength at max (T.S., MPa), elongation at break (E.B., %), and Young's modulus (MPa) were measured under normal conditions.Virgin PVC was found to be a fairly exible plastic with a tensile strength of 27.90 MPa and an elongation at break of ∼312%.By graing PVC using dapsone, remark changes in both tensile strength and elongation at break were observed to be ∼20.45MPa and 165%, respectively (Table 1).However, by adding 0.1 Ag NPs to the hybrid polymer, the ultimate strength started to increase to 21.80 MPa; then, a continuous increase was observed in the strength value by increasing the nanoparticle ratio (i.e., 0.3%) to ∼25.40 MPs.Perhaps the reason behind the achievement of this property was attributed to the reinforcing effect and the good dispersion of Ag NPs inside the hybrid matrix, leading to better interfacial bonding between the components.These ndings were evidenced by the SEM and FTIR data.Similarly, Young's modulus also increased as the quantity of Ag NPs increased.Nevertheless, the percentage of E.B. gradually reduced to ∼92.50% compared to unlled polymer matrices (Table 1)., and urea, respectively.A dose of 0.2 wt% of Ag NPs in the matrix resulted in the highest level of adsorption effectiveness.The removal effectiveness (%) of the chosen element ions was demonstrated to steadily increase as the concentration of Ag NPs increased from PVC-DAP-0.1 to PVC-DAP-0.2.This was caused by an increase in the number of functional groups that were inserted, such as sulfonyl (O]S]O), amine (-NH), and Ag NPs, which enhanced the number of active spots for element ion binding.The effectiveness of the removal was reduced as the Ag NP content increased further to 0.3 wt%.The interfacial debonding between the Ag NPs and the PVC-DAP matrix caused by nanoller aggregation was likely the cause, which reduced the membrane's reactivity.This result was consistent with that previously established for the adsorption of various ions using magnetic graphene oxide (mGO) NPs. 6Regarding the adsorption mechanism, many variables, such as pH, ionic strength, and the surface nature of the adsorbent (functional groups' active sites and surface area), can inuence the adsorption mechanism between the PVC-DAP-0.2Ag NP membrane and the selective elements (Fig. 1(a) and 4(a)).The adsorption of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 , and urea ions was controlled by surface complexations, ion exchange, and electrostatic attraction using a PVC-DAP-0.2Ag NP membrane.Reactive functional groups in the PVC-DAP-0.2Ag NP membrane absorbed negatively chartered phosphate and nitrate ions through the electrostatic force of attraction. 48During adsorption, the amine (-NH 2 ) and oxygenated group ions found in the PVC-DAP-0.2Ag NP membrane replace the harmful ions in the water through the mechanisms of ion exchange and electrostatic attraction. 49dditionally, aqueous pollutants may be pulled to the PVC-DAP-0.2Ag NP membrane through chelating, complexation, van der Waals forces, electrostatic interactions, and/or hydrogen bonding. 50The hydrophilic surfaces of PVC-DAP-0.2Ag NP membrane have amine and oxygenated groups that can easily be deprotonated to a negative charge to attract positively charged heavy metals, depending on the pH of the solution.
3.3.2.SEM analysis.SEM images exhibited the surface morphology of the fabricated membranes aer adsorption and the impact of Ag NPs on the metal ion removal efficiency inside the hybrid PVC matrix, as depicted in Fig. 5.It was obviously observed that the pores and surfaces of adsorbent-based Ag NPs were covered by metal ions, resulting in rough and porous  surfaces.Moreover, it was found that the adsorption capacity of the PVC-DAP-0.2Ag NP membrane increased compared to that of the unlled matrices or other lled nanomembranes.This outcome was supported by SEM-EDX observations, as shown in Fig. 10.
3.3.3.BET evaluation.The BET method is widely used to determine the porosity and surface area of constituents that are mesoporous and microporous.The two most important parameters in membrane elds are surface area and porosity, which indicate the membrane's functional characteristics and may even indicate potential locations for foulant build-up.The PVC-DAP and PVC-DAP-0.2Ag NP membranes, as shown in Fig. 6a and b, had type IV isotherms with type H 3 hysteresis loops that were in line with the IUPAC classication.Through capillary condensation, hysteresis loops were connected to a wide variety of physisorption isotherms.The presence of a hysteresis loop associated with the lling and clearing of the adsorbent characterizes the Type IV isotherm, which marks the beginning of multilayer formation.When the porous constituents have mesopores, the IV isotherm is common (Fig. 6a and  b).The membrane porosity increased as a result of the addition of Ag NPs to the PVC-DAP matrix.Three categories of pore sizes can be distinguished based on pore width: macropore (>50 nm), mesopore (2-50 nm), and micropore (<2 nm).As shown in Table 2 and Fig. 6c and d, it was found that the addition of Ag NPs to the PVC-DAP material backbone gradually enhanced the BET surface area, increasing the pore volume and pore size.N 2 adsorption/desorption isotherms were used to test the PVC-DAP and PVC-DAP-0.2Ag NP membrane's specic surface area and mean pore diameter.The PVC-DAP membrane's specic surface area and mean median pore diameter were measured to be approximately 20 m 2 g −1 and 52 nm, respectively.In contrast, the PVC-DAP-0.2Ag NP membrane had these values measured to be 25 m 2 g −1 and 65 nm, respectively.These results showed that the investigated membrane performance improved.3.3.4.Effect of initial concentration of selected ions and analysis of adsorption isotherms.The effects of concentrations on Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea adsorption capability onto the PVC-DAP-0.2Ag NP membrane were obtained, as illustrated in Fig. 7(a).The amount and impact of the mass resistance transfer of metallic ions between the aqueous and solid phases were overcome by the energy force offered by the concentration of metal ions. 51The percentage removal of the studied ions decreased as the concentrations of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3

−
, PO 4 3− , and urea increased from 5 to 30 mg L −1 , as observed in the plot.This nding suggests that the insufficient number of active coverage sites of the adsorbent became saturated at higher concentrations.Consequently, the concentration of metal ions at equilibrium increased as the capacity for heavy metal uptake increased.These ndings suggest that the real amount of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea ions adsorbed increased with the metal ion concentration per unit mass of the adsorbent.The adsorption capacity was calculated for the selective elements (Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea), as shown in Table 3.By increasing the initial element ion concentrations, the ratio of moles of ions to the freely available surface area of the PVC-DAP-0.2Ag NP membrane became higher, which was the cause of the reduced removal%.Similar outcomes were described for heavy metal adsorption onto Zeo/PVA/SA NC beads. 39he isotherms for adsorption describe the relationship between adsorbate concentration and their deposition onto the adsorbent surface and calculate the adsorbent's capacity for adsorption, making them crucial for adsorption investigations.Comparing various sorbents under various conditions for experimentation requires the analysis of equilibrium data on a particular adsorption isotherm.Therefore, it was crucial to determine the best correlation for the equilibrium curves.The equilibrium properties of the adsorption of metal ions in aqueous solutions were modelled using various two-parameter equations, such as those of Langmuir, 52 Freundlich, 52 Temkin, 53 and Redlich-Peterson, 54 and Table S1 † presents the equations.Fig. 7(b)-(f), respectively, illustrates the Langmuir,    , and urea onto PVC-DAP-0.2Ag NP membrane was best described by the Freundlich isotherm, suggesting that multilayer adsorption rather than adsorption onto a uniform site occurred in the system of the PVC-DAP-0.2Ag NP membrane-metal ions.It was concluded that the surface of the adsorbent changed from a homogeneous surface to a heterogeneous surface as the concentration of metal ions in the sample increased.This results in the adsorbent having a multilayer adsorption effect and interacting strongly with the ions Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , , and urea on its surface.However, the PVC-DAP-0.2Ag NP membrane's surface pores and cracks were lled with these ions, increasing the efficiency of combining active sites on the surface of the adsorbent with Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 , and urea ions.This resulted in an improvement in the adsorption capacity of the adsorbent for these ions.The ion concentration on the surface of the adsorbent increased, the critical energy of adsorption increased, and the attraction between metal ions enhanced, all of which can further increase layer adsorption capacity, as shown in the analysis in Fig. 7(c), which demonstrated that the heterogeneity constant of the Freundlich model was greater than 1.Although the R 2 for Langmuir was higher than 0.96 for all metal ions, monolayer adsorption also played a signicant role in the adsorption of the metal ions onto the PVC-DAP-0.2Ag NP membrane.The PVC-DAP-0.2Ag NP membrane was a favorable absorbent to remove Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 , and urea ions from aqueous solution because the values of the equilibrium parameter, RL, were in the range of 0 < RL < 1.The adsorption approach was favorable because the calculated RL value was less , and urea onto PVC-DAP-0.2Ag NP membranes was by chemisorption.The increased bonding energy (E, kJ mol −1 ) values found in this investigation support a chemical interaction mechanism for the interaction of the PVC-DAP-0.2Ag NP membrane with metal ions.The isotherm constants (q m and b) for the adsorption of metal ions were determined from the linear form of the D-R model, and the results are shown in Table 4.The constant values in Table 4 show that for each metal ion, the maximum sorption capacity increased as the temperature increased.A chemical phenomenon was also involved in the adsorption of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea according to the mean free energies.In general, Redlich-Peterson constant (b) values typically ranging from 0 to 1 indicate a favorable adsorption. 55The plots for this isotherm are showcased in Fig. 7(f).Values of b ((mol 2 K −2 J −2 ) × 100 000) ranged from 0.82 to 0.91 (Table 4), therefore indicating that all of the ions were favorably adsorbed by the PVC-DAP-0.2Ag NP membrane.Furthermore, the R 2 values were closer to unity for the Redlich-Peterson and Freundlich models than for the other models.Therefore, the equilibrium adsorption data for Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea ion adsorption on PVC-DAP-0.2Ag NP membrane can be represented more appropriately by the Temkin and Freundlich models in the concentration range under study.3.3.5.Effect of temperature on the selected element ions and analysis of thermodynamics parameters.The effect of temperature on Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea element ion adsorption by PVC-DAP-0.2Ag NP membrane was examined using 10 mg L −1 ion concentrations.At three temperatures 25, 35, and 45 °C, the effect of temperature on the adsorption was tested, as shown in Fig. 8(a).The temperature range used in this experiment was based on the recorded thermal groundwater temperature that was measured at the eld site (18-36.8°C) in May 2022 according to Eissa 2023. 56The results of the experiment showed that as the temperature increased from 25 °C to 45 °C, the removal efficiency improved in the case of Fe 3+ , Mn 2+ , Ni 2+ , and Pb 2+ ions.This observation was consistent with that conducted elsewhere. 57,58The mobility and penetration of metal ions within the adsorbent's porous structure might be facilitated by the higher temperature, which was the reason for this phenomenon.The kinetic energy of the metal ions increases as the temperature increases, improving their ability to move through the adsorbent material's pores.The energy barrier, oen referred to as the activation energy that metal ions must cross to be adsorbed, is removed by this enhanced mobility. 57his suggests that the sorption process of the Fe 3+ , Mn 2+ , Ni 2+ , and Pb 2+ ions is endothermic in character.Furthermore, as the temperature increased, the number of active sites on the PVC-DAP-0.2Ag NP membrane increased for adsorption.This observation was the result of a change in the pore size within the PVC-DAP-0.2Ag NP membrane's internal structure, which made it easier for the removal of metal ions.This demonstrated that the temperature signicantly affected the adsorption process in terms of the rate at which adsorbate chemicals diffuse and the size of the pores within the adsorbent materials.Consequently, increasing the temperature caused the diffusion rate to increase, resulting in a decrease in the solution's viscosity. 59,60he efficiency of removing metal ions from the PVC-DAP-0.2Ag NP membrane for investigation increases as the temperature increases.It is obvious from Fig. 8(a) that the adsorption of NO 3 − , PO 4 3− , and urea ions was negatively impacted by the increase in temperature.This suggested that the sorption process of the NO 3 − , PO 4 3− 2][63] The experimental data and relevant equations were used to analyzed the thermodynamic parameters DG °(Gibbs free energy, J mol −1 ), DH°(enthalpy of the system, J mol −1 ), and DS°(entropy, J mol −1 K −1 ) of the adsorption process of the Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea element ions (Table S1 †).The slope and intercept of the plot of ln K c vs. 1/T (Fig. 8(b)), which demonstrated linearity with good correlation coefficient values (R 2 ), were used to determine DH°a nd DS°.The values of the thermodynamic parameters DG°, DH °, and DS°at various temperatures are shown in Table 5.The negative values of DG°showed that the Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea element ion adsorption onto the PVC-DAP-0.2Ag NP membrane was feasible and spontaneous in nature.The Fe 3+ , Mn 2+ , Ni 2+ , and Pb 2+ ions appear to be more easily absorbed as temperature increases, whereas , and urea ions appear to be less absorbable as temperature increases according to the values of DG°(Table 5).The value of DG°, which increases (NO 3 − , PO 4  3− , and urea) and decreases (Fe 3+ , Mn 2+ , Ni 2+ , and Pb 2+ ) with temperature showed that the adsorption procedure was favorable at low and high temperatures, respectively.The NO 3 − , PO 4 , and urea ions were adsorbed onto the PVC-DAP-0.2Ag NP membrane with negative values for DH°and DS°, demonstrating the exothermic nature of the adsorption process controlled by physical adsorption.Randomness decreased at the solid/liquid interface throughout the adsorption procedure, reecting the DAP-0.2Ag NP membrane's high affinity for the NO 3 − , PO 4 , and urea ions.The endothermic nature of the adsorption process and the increase in randomness at the solid-liquid interface during the adsorption operation were suggested by the negative values of DH°and DS°for the Fe 3+ , Mn 2+ , Ni 2+ , and Pb 2+ ions.DH°values obtained for the adsorption of Fe 3+ , Mn 2+ , Ni 2+ , and Pb 2+ ions onto the DAP-0.2Ag NP membrane were also shown to be higher than 40 kJ mol −1 , indicating chemical adsorption.
3.3.6.Effect of contacting time on the selected element ions and analysis of adsorption kinetics.The adsorption levels of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea element ions onto the PVC-DAP-0.2Ag NP membrane as a function of interaction time are presented in Fig. 9(a).The results of the experiment's plot showed that the adsorption rate of the element ions was initially high and subsequently decreased as equilibrium approached.Consequently, the sorption capacity of the DAP-0.2Ag NP membrane increases with time.This suggests that as the adsorbate species diffuse from the bulk solution to the , and urea element ions and at 60 min for NO 3 − ions.
One of the key factors determining an adsorbent's efficacy was its adsorption kinetics, which characterized the solute absorption rate by regulating the diffusion process and the residence duration of an adsorbate at the solid/solution interface.Based on the experimental results, the linear form pseudo-1st-order and pseudo-2nd-order kinetic models were studied to determine the kind of adsorption mechanism present in the experimental system.The linear forms of pseudo-1st-order and pseudo-2nd-order kinetics models of the adsorption of the Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO and (c) were used to compute the parameters of both kinetic models (Table 6).The pseudo-2nd-order model ts the experimental data more accurately than the pseudo-1st-order model.The high R 2 values of the pseudo-2nd-order model suggested that the chemical adsorption process might occur between the DAP-0.2Ag NP membrane and Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 , and urea element ions.A better correlation (Fig. 9(b) and (c)) was conrmed by pseudo-2nd-order model theory for the experimental data, followed by intra-particle diffusion for the adsorption of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO , and urea element ions onto the DAP-0.2Ag NP membrane under study.Additionally, the computed equilibrium capacities q e (cal.) from the pseudo-2nd-order model had values that agreed well with the experimental q values q e (exp) .The intraparticle diffusion (IPD) kinetic model was employed to further study the possibility that distinct adsorption mechanisms could govern the kinetics of distinct adsorption phases.The values of k diff and C were obtained by linearly graphing q t against t 1/2 .The plot should be linear and pass through the origin if the rate-controlling step is intraparticle diffusion.The plots in Fig. 9(d) are linear, but they do not pass through the origin.This deviation from the origin or close to saturation may be caused by a change in the mass transfer rate between the start and nal stages of adsorption.Additionally, this suggests that there was initial resistance to the boundary layer and that other kinetic models may continuously affect the adsorption rate rather than intraparticle diffusion being the only step that controlled the rate.The correlation coefficient (R 2 ) and intraparticle diffusion rate constant (K diff ) were obtained from the intraparticle diffusion rate equation (Table 6).Plotting the intra-particle diffusion model against the data with an R 2 larger than 0.9 yields a straight line, as illustrated in Fig. 9(d).This demonstrated that the intra-particle diffusion method was used to adsorb Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 , and urea element ions onto the DAP-0.2Ag NP membrane, as well as the lm diffusion or other mechanisms, may be used alone or in conjunction to control the diffusion of element ion adsorption onto the DAP-0.2Ag NP membrane.These results agree with those reported elsewhere. 64,65Three mass transfer processes were included in the adsorption kinetics: the adsorbate was transferred in the liquid lm surrounding the adsorbent through external diffusion, also known as lm diffusion; the adsorbate was transferred inside the adsorbent's pores through internal diffusion, also known as intraparticle diffusion; and the adsorbate was transferred onto the active sites (Fig. 9(e)).
3.3.7.Surface structure and EDX analysis of the PVC-DAP-0.2Ag NP membrane before and aer element ion adsorption.The SEM/EDX analyses for the PVC-DAP-0.2Ag NP membrane before and aer element ion adsorption are displayed in Fig. 10(a)-(d).EDX is typically used to examine the molecular structure of solid materials.SEM is a practical method for evaluating the compatibility of various components inside polymeric materials.Using such an approach, the polymeric matrix's numerous interfaces and separation phases, which represent both mechanical and thermal stability features as well as ionic conductivity, can be found.Fig. 10(a) depicts the morphologies of the PVC-DAP-0.2Ag NP membrane before the adsorption of the selective element.Fig. 10(a) shows the construction of an ice-rock-like conguration.The SEM image in Fig. 10(a) demonstrates how the polymer sample's surface exhibits irregular small-size particles, indicating a high surface area and porous nature.Any adsorbent's large surface area allowed maximum adsorption. 66Before adsorption, the SEM images of the PVC-DAP-0.2Ag NP membrane were distinguished by its regular surface, which had pores of varying sizes and shapes, and a uniform, homogenous shape.The morphological, physical, and molecular structures of the PVC-DAP-0.2Ag NP membrane have undergone several changes as a result of the uptake and accumulation of element ions.The SEM images of the PVC-DAP-0.2Ag NP membrane aer adsorption showed noticeable modications in its morphology, including clear deformation, indentations in the PVC-DAP-0.2Ag NP membrane, denser, packed tightly, and clear and irregular pores.Fig. 10(c , and urea element ions, revealing the existence of C, O, N, Ag, S, and Cl as the main components.Fig. 10(d) displays the appearance of new peaks to conrm the adsorption of Fe 3+ , Mn 2+ , Ni 2+ , and Pb 2+ ions, verifying that it was adsorbed successfully by the PVC-DAP-0.2Ag NP membrane.Fig. 10(d) illustrates that a small peak of phosphorus was present, showing that it was adsorbed effectively by the PVC-DAP-0.2Ag NP membrane, and the peaks of nitrogen increased, conrming the effective adsorption of NO 3 − and urea.
3.3.8.Regeneration studies and reusability.The evaluation of the adsorption material's economical and environmentally benecial qualities requires regeneration.Desorption and reproducibility in the adsorption process are crucial factors for creating novel adsorbents with practical applications.An important phase in the treatment of contaminated water is the regeneration of the adsorbents employed to extract metal ions. 39ecause the PVC-DAP-0.2Ag NP membrane could be employed in all four cycles without changing appearance, the regeneration investigation demonstrated remarkable mechanical stability.The amount of adsorption somewhat decreased aer each cycle., and urea, respectively, of their initial adsorption capacity aer four succeeding adsorption/desorption cycles, which conrmed their effective recoverability.The greatest percentage of element ion adsorption was determined to be in the following sequence order: Fe 3+ > Pb 2+ > Ni 2+ > Mn 2+ > NO 3 − > PO , and urea from contaminated water.3.3.9.Contaminated groundwater remediation.For humans and all other living things, water is the source of life.The New Valley is one of Egypt's largest governorates, accounting for roughly 44.0% of the country's total land area and 56% of its western desert regions. 67Only subsurface water, which originates from the Nubian Sandstone Aquifer, is the main water supply in this region.As a result of the Nile Valley region's inadequate rainfall, underground water in this region has emerged as the primary and possibly the only source for domestic and agricultural uses. 68The sediments contained , and Pb 2+ demonstrated potential health risks to humans.According to earlier research, the main exposure method to potentially hazardous elements is by ingesting food and drinking water. 70hese metals can pose signicant risks to human health because they are exposed to people through various mechanisms, including ingestion, oral absorption, and cutaneous absorption. 71Therefore, it is important to assess the dangers associated with using these subsurface waters for drinking and irrigation.To prevent potential persistent health risks for both children and adults, purifying water before use should be considered in many regions of the New Valley., and urea ions from the area's polluted water resources in New Valley.The removal efficiency ranged from 12 to 98% using PVC-DAP-0.2Ag NP membrane (Table 7).The rejection percentages of the TDS, Ca 2+ , Mg 2+ , Na + , K + , HCO The reduction in the concentricity of major, minor, and trace elements was subsequently a large decline in the salinity of the treated groundwater samples, which reached 46%.The PVC-DAP-0.2Ag NP membrane created can therefore be advised for use in treatment and desalination processes.One of the key environmental pollutants that had an impact on how various body organs function was heavy metals.The presence of heavy metals in drinking water (surface, ground, and ocean) is a concern for human health and can cause both cancer and non-cancer ailments. 5The kidney is the rst organ affected by heavy metal poisoning due to its capacity to reabsorb and accumulate divalent metals.The primary kidney damaging heavy metals can result in tubular damage and glomerulopathies are Cr 2+ , Cd 2+ , Pb 2+ , Hg 2+ , Cu 2+ , U 2+ , As +3 , and Bi 3+ . 72t is observed that most residents of the New Valley suffer from some health problems as a result of the high levels of heavy elements, especially Al 3+ , Fe 3+ , Cr 2+ , Mn 2+ , Ni 2+ , and Pb 2+ , in the groundwater used, whether for drinking or agriculture, causing some chronic diseases, especially kidney failure.The study with PVC-DAP-0.2Ag NP membrane proved that they were able to get rid of heavy and minor elements from the wastewater in the New Valley region, whether ground or surface, which may greatly affect the kidneys, heart and brain.Therefore, it is recommended that these membranes be used as lters for patients with renal failure because they have proven to be highly efficient in removing toxic metals, as well as phosphate, nitrate groups, and urea.

Antibacterial assay
The antibacterial test for virgin PVC, PVC-DAP and their nanocomposites with varying proportions of Ag NPs was carried out  to assess these materials utilized as nanomembranes for water remediation or biomedical purposes, such as dialysis devices. 73his assay was performed against two severe bacteria, such as K. pneumonia (i.e., G − bacteria) and S. aureus (i.e., G + bacteria).The obtained ndings reported in Fig. 12 revealed that virgin PVC and its hybrid negatively affected the growth of selected bacteria in the experiment.Besides, their inhibition zones in the Petri dish were almost zero for the selected bacteria although DAP itself has biological activity for acne treatment as veried elsewhere. 74In contrast, halos of inhibition were noticed for nanomembranes with different diameters ranging from ∼6.50 to 14 mm depending on the bacterial type and the Ag NP ratio in the matrix, as shown in Fig. 12 and Table 8.This enhancement was due to the presence of Ag NPs, which were effectively active in hindering the growth of a wide range of G − and G + bacteria by interrupting bacterial developments. 8,29,75

Fig. 1
Fig. 1 (a) Schematic representation showing the hybridization process of PVC by DAP to fabricate nanomembrane-based Ag NPs and (b) adsorption mechanism of heavy metal ions on the membrane surface.

Fig. 2
Fig. 2 (a) Zeta potential of Ag NPs and their particle size distribution (b).

Fig. 3
Fig. 3 (a) FTIR spectra of virgin PVC, hybrid PVC, and the nanocomposites; (b) XRD patterns of pure DAP, virgin PVC, PVC-DAP, and nonabsorbent films containing varying quantities of Ag NPs.

Fig. 5
Fig. 5 SEM images of virgin PVC, PVC-DAP and the nanocomposites containing various Ag NP proportions after adsorption at 5000×.

© 3 −
2024 The Author(s).Published by the Royal Society of Chemistry RSC Adv., 2024, 14, 19680-19700 | 19691 Paper RSC Advances adsorbent surface, the number of pores on the adsorbent's active binding centers increases, reducing the mobility and availability of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO the DAP-0.2Ag NP membrane media.Quick adsorption may be due to contacts of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3 − , PO 4 3− , and urea element ions with obtainable surface adsorption spots onto the DAP-0.2Ag NP membrane, whereas the subsequent gradual adsorption may be caused by the selective element being taken up into the pores of the adsorbents.Equilibrium was reached at 45 min for Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , PO 4 3−

Table 1
Mechanical parameters derived from tensile testing for hybrid PVC-DAP absorbent films

Table 2
BET measurements of PVC-DAP and PVC-DAP-0.2Ag NPs Table4illustrates a list of the different adsorption isotherm model parameters and the linear regression coefficients, R 2 .It can be observed that the R 2 values were much closer to unity for the Freundlich and Temkin models than for the other two.Therefore, the Temkin and Freundlich models can best describe the adsorption data of Fe 3+ , Mn 2+ , Ni 2+ , Pb 2+ , NO 3

Table 7
Chemical analyses of major, minor, and trace elements in the contaminated groundwater sample before and after treatment using the PVC-DAP-0.2Ag NP membrane